Geology

Paleontological Resources

The Channel Islands, particularly San Miguel, Santa Rosa, and Santa Cruz, contain numerous plant and animal fossils that illuminate the past natural history of the California coastal region. This fossil record offers the opportunity to study fauna speciation and evolution, the development of plant and animal communities, their adaptations to varying climate conditions, and the effects of human colonization on the fauna. As a result, the Channel Islands are of special interest to researchers, and a number of paleontological studies have been done on the islands.

Research indicates that the Pleistocene fauna of the Channel Islands is unique in several respects. First, it contains several extinct species, including pygmy mammoth, an owl, a flightless goose, a puffin, and a vampire bat, and two species of giant mouse. The park also contains the best representation of Pleistocene marine avifauna on the Pacific coast, with over 70 species having been discovered on San Miguel.

The most notable animal fossils, and the best studied aspect of island paleontology, are the pygmy mammoth (Mammuthus exilis). Remains of this species have been known on the Channel Islands since 1856 when they were discovered by a coast and geodetic survey. In 1994 a nearly complete adult skeleton was discovered and excavated on Santa Rosa. Pygmy mammoths descended from full-sized Columbia mammoths that swam across the Santa Barbara Channel to the islands during the Pleistocene. It is believed that during that period the northern Channel Islands were connected into one large island because of the lowered sea levels. Apparently pygmy mammoths died off at about the end of the Pleistocene (12,000 years ago). Pygmy mammoth fossil bones have been found on more than 140 sites on San Miguel, Santa Rosa, and Santa Cruz. These are the only known remains in the world. On Santa Rosa, fossils are often exposed in sands, silts, and gravels of Pleistocene age anywhere on the island. Most specimens have been found in the sediments comprising the coastal terraces of the island. Due to the numerous questions about many aspects of this species' evolution and development, any fossil may potentially be of crucial importance in answering important research questions.

Another important paleontological resource is the caliche fossil forests, or rhizoconcretions, on San Miguel. Three major caliche forests are found on the island. These fossils are calcium carbonate-encrusted casts of vegetation buried by sand dunes more than 14,000 years ago. They provide evidence that the island once supported large trees and shrubs. These caliche casts are fragile and easily broken.

The Channel Islands are a continuation of the Santa Monica Mountains on the main­land, though they were never connected above sea level, and are composed of many of the same Tertiary marine formations. As such, they also have many of the same marine invertebrate fossils. Although there are studies on the invertebrate paleontology of these formations in the Santa Monica Mountains, there has not been research done on their counterparts on the islands. There have been some studies of the Pleistocene invertebrate fauna of the islands, but as is the case of the invertebrates from the Tertiary marine sediments much remains to be done.

Although researchers have learned quite a bit about some of the park's fossils, such as the pygmy mammoth, paleontological resources on the Channel Islands have not been very well studied. Fossil localities containing smaller terrestrial species of Pleistocene age and invertebrate fossils embedded in the Miocene strata of the islands remain unstudied. In addition, natural and human-induced erosion probably has degraded or destroyed fossil sites; unless collected properly and promptly, bones that are exposed by erosion may be scattered and lost.

Kelp Forests

Ecology and Importance

Kelp forests are true forests providing shelter and food for over 1,000 species of animals and plants that live within them. Fish such as rockfish, kelp bass and California Sheephead hide among kelp fronds to avoid predators and to search for smaller prey. The tall fronds rising to the surface provide substrate and protection for many invertebrate species. Others, like the sea urchins, wavy turban snails, and abalone are there to dine on the kelp blades.

Giant kelp, Macrocystis pyrifera, may grow at depths below 100ft, sending their leaf like fronds to the surface to create a dense canopy. Holdfasts, root like structures that anchor the kelp to the bottom, are excellent hiding places and act as nurseries to juvenile invertebrates such as spiny lobster, sea cucumber, and sea urchins. The blades of kelp help slow water movement within the kelp forest, providing more refuges for smaller organisms such as juvenile rockfish.

Kelp forests of the Channel Islands experience both warm water currents from the South and cold water currents from the North. This mixing of currents creates a highly productive system and a diversity of organisms that is only found over a much greater area of the California coast. Some examples of warmer water species include Garibaldi, moray eels, and the spiny lobster. Examples of colder water organisms include black rockfish, and the sunflower star.

Kelps are harvested for alginates, products that are used as thickeners and stabilizers in many foods and other products from ice cream to soaps and shampoos. Kelp forests also provide the diversity, color, and structure that make them a favorite of divers and photographers.

Rocky Intertidal Zone

Undisturbed tidepools are one of the many exquisitely rich seascapes greeting a visitor who ventures into an island's splash zone at Channel Islands National Park. Covered and uncovered twice each day by tides, the Park's rocky intertidal (roughly meaning "between tides") is home to an abundance and diversity of marine life, unparalleled by even the most unspoiled, remote shorelines along California's mainland.

Few other places promise such a captivating and wonderful array of marine life in such a relatively short distance - from the lush intertidal algal and plant growth that provide habitat for so many marine animals, to the strange and wonderful invertebrate creatures that lie beneath. Whether exploring the tideline by foot, kayak or snorkel, or just spending an hour or two with a naturalist at the pier on East Anacapa Island, one can't help but come away with an heightened appreciation of just how remarkably rich and diverse these islands are for its intertidal (and subtidal) habitats and inhabitants!

Several major factors contribute to the richness of sea life around the Channel Islands: 1) their location near the boundary of two major biogeographic provinces (the Oregonian and the Californian); 2) their diversity of habitat types and exposure to varying oceanographic conditions; 3) their high productivity resulting from upwelling of cold nutrient-rich water off Pt. Conception; and 4) their isolation from the mainland, leaving the islands' coastline further removed from the risks of some human-induced impacts.

However remote, trampling by visitors, harvest of resources, foraging and/or invasion by alien species, and episodic (or chronic) pollution including oil spills remain the biggest threats to this fascinating group of marine flora and fauna occurring among the islands' remote rocky intertidal boulder fields, headlands, sandy beaches, and within surfgrass or kelp-dominated habitats. These strangely wonderful plants and animals - mostly resilient and adapted to the rise and fall each day of the tide and to the variable nature of the area's ocean currents - remain ever vulnerable to rapid and/or irreversible changes affecting the adjacent marine ecosystem.